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Discussion Starter #1
So took the car on the freeway for the first time since the steering issue. Got going about 60 mph and I got this wicked vibration. It was bad enough I had to slow down to 45 mph and get off at the next exit. To me and my passenger it felt like it was coming from the rear end and it felt like the rear wheels were going to fall off. The faster I got going the worse it got. This is my drivetrain: 302, 3 speed manual, stock driveshaft, 8 inch with 2.79 gear ratio. Can anyone give me a bit of feedback as to what this could be? My guesses are:
1. Bad differential
2. Driveshaft not balanced.
3. Maybe the engine because someone put the wrong flywheel on it and it vibrated pretty badly however I fixed it and it runs and drives with no vibration whatsoever under 45 mph.

It starts to get bad giving it full throttle in 3rd gear. I first thought this was the transmission but now, since it felt like it was coming from the rear end. I've been wanting to change out the gears for some time so maybe this is a good thing ;)
 

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If it's only with road speed and not engine speed, you can rule out the flywheel. The most common cause of rear end vibrations is an unbalanced driveshaft, while bad bearings can also cause similar issues, as well as flat-spotted tires. Does it come with much noise? For instance, do you notice much moaning or grinding, or other smaller vibrations that are also speed related?
 

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It could be lots of things. But if it increases with speed almost for sure a balance issue. Look at the drive shaft and both wheels for signs of a missing weight. Could be a simple as the tires were never or need to be balanced. Unless the car had been in a crash it is very unlikely it is bent axles, they leak not vibrate. Also not likely the rear end is at fault, they make noise when bad. Now something could be loose causing the imbalance.
 

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Discussion Starter #4
If it's only with road speed and not engine speed, you can rule out the flywheel. The most common cause of rear end vibrations is an unbalanced driveshaft, while bad bearings can also cause similar issues, as well as flat-spotted tires. Does it come with much noise? For instance, do you notice much moaning or grinding, or other smaller vibrations that are also speed related?
Tires are practically brand new so I doubt it's that even though they weren't balanced as far as I know. I don't have any moaning or grinding at all at other speeds so I'm assuming it's a driveshaft problem. How hard is it to replace u joints? Could I do it myself or should I have a professional shop do it?
 

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How can you say it is not the tires when you are not sure they were balanced. Balancing puts the whole rotating combination of the tire, wheel, and stem at equilibrium. No vibration.
 

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Discussion Starter #6
How can you say it is not the tires when you are not sure they were balanced. Balancing puts the whole rotating combination of the tire, wheel, and stem at equilibrium. No vibration.
I would just never think something so small could create such a huge problem. I'm going to get the tires balanced today and install new u joints. Will report back
 

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Discussion Starter #7
Turns out it was indeed the u joints on the driveshaft. Got it going 80+ on the highway today. Always fun! :)
 
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